There are large warehouses regularly available all along I-95 in New Jersey. They also may not need as huge of a footprint as you think - I believe they have some large warehouses just across the border in PA as well (<2 hours away), so this one may only be critical for same day delivery. Yes, it would be expensive, more expensive than closing a Wal-Mart store, but I wouldn't be surprised if Amazon finds the alternative worse.